An alternative method for exciting waves in bars for calibration of accelerometers

Ausgangspunkt der Arbeit war, dass mit verfügbaren Erregern zur stoßförmigen Kalibrierung von Beschleunigungsaufnehmern mit Amplituden > 5.000 m/s² nicht komplett zufriedenstellend kalibriert werden kann. Hier wird üblicherweise das Hopkinson-Stab-Prinzip eingesetzt. Dieses Prinzip basiert auf der Wellenausbreitung in einem langen, dünnen Stab. Die Welle wird mit einem mechanischen Kraftstoß erzeugt. Herkömmliche Hopkinson-Stab-Kalibriererreger lassen sich aufgrund des mechanischen Aufbaus schwer steuern. Aus dem mechanischen Aufbau resultieren weiterhin Verschleiß sowie mangelhafte Reproduzierbarkeit als negative Eigenschaften. Das Ziel der Arbeit war folglich, den mechanischen Kraftstoß durch eine alternative Methode zur Anregung von Wellen in Stäben, bzw. eine elektrisch steuerbare Aktorik, zu ersetzen. Ein Hauptteil der Arbeit war die Erstellung eines Modells des klassischen Hopkinson-Stabes. Der nächste Schritt war die Auswahl geeigneter Aktorik zur Erzeugung eines dem Kraftstoß analogen Kraft-Zeit-Verlaufs. Mit einem geeigneten Aktor (piezoelektrisches Prinzip) erfolgte der Aufbau eines prototypischen Kalibriererregers. Die Untersuchung und Vermessung des Prototypen zeigte, dass der Ansatz der Arbeit, den mechanischen Kraftstoß durch eine elektrisch steuerbare Aktorik zu ersetzen, in einem großen Parameterfeld realisiert worden ist. Die Probleme, wie Abhängigkeit der Beschleunigungsdauer von der Beschleunigungsamplitude, mangelhafte Reproduzierbarkeit oder Verschleiß, die sich bei konventionellen mechanischen Systemen ergeben, sind mit dem erarbeiteten Aufbau nicht mehr existent. Die elektrisch präzise steuerbaren stoßförmigen Beschleunigungssignale stellen eine Neuheit auf diesem Gebiet der Kalibrierungen dar und eröffnen dem Anwender damit völlig neue Möglichkeiten.The starting point was that with available exciters for shock calibration of accelerometers with amplitudes> 5.000 m/s² can be calibrated not completely satisfactory. Here usually the Hopkinson-Bar principle is used. This principle bases on the wave propagation in a long, thin rod. The wave is generated by a mechanical force impact. Conventional Hopkinson-Bar calibration exciters can be controlled difficult due to the mechanical structure. From the mechanical structure also result wear and poor reproducibility as negative characteristics. Consequently the aim of this study was the replacement of the mechanical force impact by an alternative method for excitation of waves in bars – this means her an electrically controllable actuator. A major part of this work was to develop a model of the classical Hopkinson-Bar. The next step was the selection of appropriate actuators for generating a Force-Time-Signal analogue the mechanical force impact. With a suitable actuator (piezoelectric principle) a prototype calibration exciter was build. The investigation of and measurements on the prototype showed that the approach of the work, the replacement of the mechanical impact by an electrically controllable actuators, have been implemented in a large parameter field. The problems, e.g. dependency of the acceleration pulse width from acceleration amplitude, poor reproducibility or wear, that are existent in conventional mechanical systems do no more exist in the new developed exciter. The precise electrically controllable shock acceleration signals are a novelty in this field of calibrations and present completely new possibilities to the user

Particle Swarm Optimization for Energy Disaggregation in Industrial and Commercial Buildings

This paper provides a formalization of the energy disaggregation problem for particle swarm optimization and shows the successful application of particle swarm optimization for disaggregation in a multi-tenant commercial building. The developed mathmatical description of the disaggregation problem using a state changes matrix belongs to the group of non-event based methods for energy disaggregation. This work includes the development of an objective function in the power domain and the description of position and velocity of each particle in a high dimensional state space. For the particle swarm optimization, four adaptions have been applied to improve the results of disaggregation, increase the robustness of the optimizer regarding local optima and reduce the computational time. The adaptions are varying movement constants, shaking of particles, framing and an early stopping criterion. In this work we use two unlabelled power datasets with a granularity of 1 s. Therefore, the results are validated in the power domain in which good results regarding multiple error measures like root mean squared error or the percentage energy error can be shown.Comment: 10 pages, 13 figures, 3 table

A Non-Intrusive Load Monitoring Approach for Very Short Term Power Predictions in Commercial Buildings

This paper presents a new algorithm to extract device profiles fully unsupervised from three phases reactive and active aggregate power measurements. The extracted device profiles are applied for the disaggregation of the aggregate power measurements using particle swarm optimization. Finally, this paper provides a new approach for short term power predictions using the disaggregation data. For this purpose, a state changes forecast for every device is carried out by an artificial neural network and converted into a power prediction afterwards by reconstructing the power regarding the state changes and the device profiles. The forecast horizon is 15 minutes. To demonstrate the developed approaches, three phase reactive and active aggregate power measurements of a multi-tenant commercial building are used. The granularity of data is 1 s. In this work, 52 device profiles are extracted from the aggregate power data. The disaggregation shows a very accurate reconstruction of the measured power with a percentage energy error of approximately 1 %. The developed indirect power prediction method applied to the measured power data outperforms two persistence forecasts and an artificial neural network, which is designed for 24h-day-ahead power predictions working in the power domain.Comment: 15 pages, 14 figures, 4 table

Rare Variants in PLXNA4 and Parkinson's Disease.

Approximately 20% of individuals with Parkinson's disease (PD) report a positive family history. Yet, a large portion of causal and disease-modifying variants is still unknown. We used exome sequencing in two affected individuals from a family with late-onset familial PD followed by frequency assessment in 975 PD cases and 1014 ethnically-matched controls and linkage analysis to identify potentially causal variants. Based on the predicted penetrance and the frequencies, a variant in PLXNA4 proved to be the best candidate and PLXNA4 was screened for additional variants in 862 PD cases and 940 controls, revealing an excess of rare non-synonymous coding variants in PLXNA4 in individuals with PD. Although we cannot conclude that the variant in PLXNA4 is indeed the causative variant, these findings are interesting in the light of a surfacing role of axonal guidance mechanisms in neurodegenerative disorders but, at the same time, highlight the difficulties encountered in the study of rare variants identified by next-generation sequencing in diseases with autosomal dominant or complex patterns of inheritance

Involvement of the subthalamic nucleus in engagement with behaviourally relevant stimuli

In this study we investigate how the basal ganglia (BG) may process the behavioural relevance of environmental cues by recording local field potentials (LFPs) in the subthalamic nucleus of patients with Parkinson’s disease who had undergone implantation of electrodes for deep brain stimulation. Fourteen patients were recorded as they performed a paradigm dissociating warning cue presentation from programming related to execution of specific tasks. Target and non-target warning cues of differing behavioural relevance were contrasted, and we evaluated if warning cue-evoked activities varied according to whether the eventual task to be performed was motor or cognitive and whether patients were receiving or withdrawn from dopaminergic therapy. Warning cues evoked a complex temporal sequence of activities with three epochs over the 760 ms following the onset of the warning cue. In contrast to the initial evoked LFP, evoked activities over two later periods were significantly influenced by behavioural relevance and by treatment state. The early activity was likely related to the initial orientating of attention induced by a novel target, while the delayed responses in our paradigm may reflect processing related to the non-motor resource implications of cues. The results suggest that the BG are intimately involved in the evaluation of changes in the environment and of their behavioural significance. The latter process is partly modulated by dopamine. Weakness in this function might contribute to the behavioural impairment that can follow BG lesions and surgery

Characterisation of development and electrophysiological mechanisms underlying rhythmicity of the avian lymph heart

Despite significant advances in tissue engineering such as the use of scaffolds, bioreactors and pluripotent stem cells, effective cardiac tissue engineering for therapeutic purposes has remained a largely intractable challenge. For this area to capitalise on such advances, a novel approach may be to unravel the physiological mechanisms underlying the development of tissues that exhibit rhythmic contraction yet do not originate from the cardiac lineage. Considerable attention has been focused on the physiology of the avian lymph heart, a discrete organ with skeletal muscle origins yet which displays pacemaker properties normally only found in the heart. A functional lymph heart is essential for avian survival and growth in ovo. The histological nature of the lymph heart is similar to skeletal muscle although molecular and bioelectrical characterisation during development to assess mechanisms that contribute towards lymph heart contractile rhythmicity have not been undertaken. A better understanding of these processes may provide exploitable insights for therapeutic rhythmically contractile tissue engineering approaches in this area of significant unmet clinical need. Here, using molecular and electrophysiological approaches, we describe the molecular development of the lymph heart to understand how this skeletal muscle becomes fully functional during discrete in ovo stages of development. Our results show that the lymph heart does not follow the normal transitional programme of myogenesis as documented in most skeletal muscle, but instead develops through a concurrent programme of precursor expansion, commitment to myogenesis and functional differentiation which offers a mechanistic explanation for its rapid development. Extracellular electrophysiological field potential recordings revealed that the peak-to-peak amplitude of electrically evoked local field potentials elicited from isolated lymph heart were significantly reduced by treatment with carbachol; an effect that could be fully reversed by atropine. Moreover, nifedipine and cyclopiazonic acid both significantly reduced peak-to-peak local field potential amplitude. Optical recordings of lymph heart showed that the organ’s rhythmicity can be blocked by the HCN channel blocker, ZD7288; an effect also associated with a significant reduction in peak-to-peak local field potential amplitude. Additionally, we also show that isoforms of HCN channels are expressed in avian lymph heart. These results demonstrate that cholinergic signalling and L-type Ca2+ channels are important in excitation and contraction coupling, while HCN channels contribute to maintenance of lymph heart rhythmicity

Loss of thalamic serotonin transporters in early drug-naïve Parkinson’s disease patients is associated with tremor: an [123I]β-CIT SPECT study

In vitro studies revealed serotonin transporter (5-HTT) decline in Parkinson’s disease (PD). Yet, few studies investigated thalamic 5-HTT in vivo and its effect on PD heterogeneity. We analyzed thalamic [123I]β-CIT binding (mainly reflecting 5-HTT binding) in 32 drug-naïve PD patients and 13 controls with SPECT. Twenty-six patients were examined twice (17 months apart). Based on UPDRS scores, we identified subgroups of patients with moderate/severe tremor (PDT) and without tremor (PDWT) at the time of clinical diagnosis. Additionally, depressive symptoms were evaluated using the Beck Depression Inventory (BDI) at baseline. Mean thalamic specific to non-specific [123I]β-CIT binding ratio was lower in patients when compared to controls, and further decreased during follow-up. At baseline, average thalamic ratio was significantly lower in the PDT than in the PDWT subgroup. No correlation was found between BDI scores and thalamic binding ratios. Our findings show decline of [123I]β-CIT binding to thalamic 5-HTT in PD and its possible contribution to tremor onset